S of focalized laser rays apparatus for cutting slivers of continuous textile filaments by mean

ABSTRACT

A method and equipment for cutting slivers of continuous filaments of textile material into tuft fibres adapted for further spinning and twisting operations, wherein a continuous sliver formed by said filaments is advanced at a high speed in a plane and laser ray pulses are focalized on said plane in the form of a narrow window having a length greater than the width of said sliver, in order to cut the same into a plurality of tuft fibres having a predetermined length.

0R answer? lite States Patent 1 1 3,757,077 Siciari et al. Sept. 4, 1973APPARATUS FOR CUTTING SLIVERS OF OTHER PUBLICATIONS Laser MachineDisclo- MEANS OF FOCALIZED LASER RAYS sure Bulletin Vol. 8, No. 6, 11/65pp. 881 [75] Inventors: Francesco Siclari; Franco Magnoni; Laser li iIEEE Spectrum May, 1968 pp.

Glancarlo Bianucci, Mllan, Italy g [73] Assignee: Snia i wazfonale C02Applications" Coherent Radiation Laboratory lndustrla Appllcazlonlvlscosa, Brochure Sept, 1969 Milan, Italy Introduction to Gas Jet LaserCutting Metal Con- [22] led: 1971 struction and British Welding JournalJanuary, 1970, [21] Appl. No.: 126,787 pp. l-8

[30] Foreign Application Priority Data im ry Ex miner-R. F. Staubly Mar.26, 1970 Italy 2221932470 4mm"! Examiner-George MmmmyeAttorney-Wenderoth, Lind & Ponack [52] lU.S. CI. 219/121 L, 19/3, 19/6[51] Int. Cl B231: 27/00 58 Field of Search 219/121 L, 121 EB, [57]ABSTRACT 19/3, 6; 57/2 A method and equipment for cutting slivers ofcontinuous filaments of textile material into tuft fibres adaptedReferences Cited for further spinning and twisting operations, wherein aUNITED STATES PATENTS continuous sliver formed by said filaments isadvanced 2,278,032 3 1942 Youngman 57/2 at a high Speed in a Plane andlaser y Pulses are focal- 3,634,646 1/1972 Ber er 219/121 L ized on saidplane in the form of a narrow window hav- 3,483,780 12/1969 Hudson83/325 X ing a length greater than the width of said sliver, in3,532,466 1971 Quirk 219/121 LA order to cut the same into a pluralityof tuft fibres hav- 3,512,437 5/1970 Enneper et al. 83/325 i apredetermined length. 2,851,103 4/1958 Anthony et al. 83/913 6 Claims, 2Drawing Figures L A S E R DRI V E CONTROL CONTROL 0 PMENTEDS" 3.751; 077

LASER DRIVE CONTROL CONTROL FRANCASCO SICLARI=,:

FRANCO MAGNONI &

GIANCARLO BIANUCCI,

INVENTOR. s

Attorney APPARATUS FOR CUTTING SLIVERS OF CONTINUOUS TEXTILE FILAMENTSBY MEANS OF FOCALIZED LASER RAYS BACKGROUND This invention generallyrelates to the problem of cutting textile and in particular syntheticcontinuous filaments into more or less short fibres in order to obtainso called tuft fibres adapted for further spinning and twistingoperations, as required for producing fibrous textile yarns.

As well known, all artificial and synthetic fibres are produced in theform of continuous filaments extruded through spinnerets and thensuitably drawn or otherwise processed, said filaments being gathered andadvanced in the form of slivers (wherein said filaments are arrangedparallel and close to, but not connected with each other), consisting ofa very large number (usually many thousand) of filaments. Such slivers,or more exactly all filaments thereof are cut into preestablishedlengths to form said tuft fibres which are then forwarded toconventional processes in order to obtain a rove whereon spinning andtwisting operations are carried out.

The most modern techniques for producing artificial and syntheticfilaments allow the attainment of very high sliver feeding speeds, ofthe order of several hundred meters per minute, and a trend to furtherincrease said speeds can also be noticed. Since the filaments to beconverted into tuft fibres are to be cut into very short lengths (ofabout 40 mms for a so called cotton cut, and about 70-90 mms for awoollen cut), the cutting frequency may attain very high values, of theorder of several thousand cuts per minute and therefore of many hundredcuts per second.

According to the known art, a cutting operation is carried-out onfilament slivers by mechanical means and in particular by suitable shearblades or knives that act on the sliver in a point intermediate betweentwo points thereof wherein the filaments are retained or anchored. Suchaction is usually performed by engaging and advancing the sliver betweencounterrotating members, generally in the form of suitably groovedrollers, metal chains or the like. The filaments are thus engagedbetween the sharp corners of slots or grooves of said rotary members,one or both of which may comprise edges of a resilient material in orderto ensure the adherence and detainment of filaments. Downstream of thecutting point, an air stream or other suitable means draws away the thusobtained tuft fibres.

Such mechanical systems are rather complicated and the high speeds andcutting frequencies as required in the actual production of said fibresare hardly attained. in addition, the artificial filaments and inparticular the synthetic ones as e.g. polyester filaments, may be ratherhard and then cause a very quick wear of blade or knive cutting edges,which results in a necessity to frequently replace the cutting tools andthus to stop the cutting equipment.

In addition, said blades or knives may become further worn due to thepossible presence of acidic components in the filaments, when obtainedfrom spinning rayon or regenerated cellulose.

in addition to said increase in the silver linear speed, the most moderntechnique trends to gather an ever in creasing number of filaments intoa single sliver, until obtaining slivers formed of filamentsindividually having a very small count (e.g. 1 or 2 deniers) but showingon the whole very big counts, of the order of a few millions of deniers(weight in grams of 9,000 meters of textile material).

An object of this invention is to provide, in the field of cuttingslivers consisting of a very high number of single filaments andadvancing at very high linear speeds, a method by which already knowndrawbacks and restrictions of prior art mechanical cutting systems arewholly overcome. A more specific object of this invention is to find andindustrially carry-out'the scientific principle of obtaining a very highand strictly localized thermal action by means of focalized laser rays(coherent monochromatic light energy).

In the textile industry it is well known to use laser rays to cutfabrics, carpets and similar laminar-shaped textile products, but thiscutting operation is carriedout over a great fabric length and then at areduced speed.

Under these conditions the thermoplastic filament ends may stick witheach other and this occurrence is not considered as harmful; on thecontrary, at least from certain viewpoints said sticking action may beconsidered as suitable in that it stabilizes the cut fabric edges.

However the problem to cut filament slivers into short fibres differsfrom above in that the filament feeding speeds are very high and thecutting time is consequently reduced; further, a filament end stickingaction would be very harmful.

SUMMARY According to this invention, it has been surprisinglyascertained that a laser radiation, when focalized in an essentiallyrectangular window having a major side directed crosswise to the sliverfeeding direction and longer than the sliver width, as well as a minorside of a few microns only, and when said radiation is applied in theform of pulses having a pulse duration of a few millionth of second, isable to sharply and thoroughly I cut all filaments in the sliver, with acomplete removal of material in front of said window and without causingundesirable melting phenomena in the zones adjacent to the cut as wellas welding phenomena on the fibres closely contacting with one anotherduring said cutting operation.

In particuiar, the method according to this invention consists infeeding a filament sliver at a required linear speed, between twocounter-rotating feeding elements, and in particular between paralleland closely adjacent lengths of two endless chain tracks, at least oneof which is formed with windows uniformly spaced at intervals equal tothe length or to a submultiple of the length of fibres into which thefilaments are to be cut, and in directing on said sliver a pulsed laserray focalized toward the plane wherein the sliver is lying, insynchronism with the passage of said windows across the point whereinthe sliver feeding direction intersects the direction of said laser ray.

Laser pulses synchronized with the passage of said windows can beobtained by placing a suitable intercepting device, e.g. in the form ofa suitably perforated rotating disk, in the path of rays continuouslyemitted by a generator, or preferably by providing a pulse generatorhaving a frequency synchronized with that of said cutting cycle, andmore precisely a frequency as follows:

f sliver feeding speed/cut length (or fibre length) said synchronismbeing obviously pre-set in such a manner that said focalized ray pulsesstrike the sliver at the moment wherein it appears uncovered through awindow of said feeding track system.

According to a preferred embodiment of this invention a laser ray sourceis used that emits a radiation having a wavelength corresponding to oneof the ab sorption bands of the polymer forming the filaments to be cut,and preferably corresponding to the more relevant absorption band. Saidabsorption bands are generally very narrow and it has been ascertainedthat changes in the laser ray wavelength, even of fractions of microns,may considerably affect the cut efficiency. On the contrary, when alaser ray having a wavelength corresponding to the more relevant polymerabsorption band is provided, the cut operation may be performed at ahigh speed and without any harmful fibre sticking.

According to a further feature of this invention, said method alsocomprises to blow an inert gas and in particular nitrogen against sliverpoints directly upstream and downstream the cut line, in order to ensurean instantaneous heat removal from the filament and fibre zones directlyadjacent to said out (wherein the filament material is melted or moreexactly volatilized), as well as to ensure that the cutting operation bemade in an environment wherein no oxidation phenomena due to thepresence of atmospheric oxygen may occur.

DRAWING FIG. 1 is a perspective view of the whole equipment, and

FIG. 2 is an enlarged detailed view of the cutting zone of saidequipment.

PREFERRED EMBODIMENT The shown equipment comprises a laser generator,generally designated by the numeral and operating to emit a ray througha window 12, having a few millimeters light diameter, in a direction asindicated by the dot and dash line 14. Said generator comprises suitablefocalizing systems well known in the art and therefore not shown, bywhich said laser ray is focalized or concentrated at a pre-establishedfocal length in the form of a flat and lengthened beam, directed towarda rectangular window 16 (see FIG. 2), having a major side slightlylonger than the width of the sliver 18 to be cut.

The sliver 18 is fed at a linear speed V between two counter-rotatingendless chain tracks 20 and 22 having parallely fitted sections locatedat a right angle in respect to the laser ray direction 14. Said endlesschain tracks are guided at a linear speed V by pairs of pulleys 24, 26and 28 and 30, respectively, at least one pulley of each pair beingsuitably driven. Said tracks 20 and 22 may be in the form of metal bandsor non-metallic material bands, and are supported in such a manner as toshow parallel and approached lengths 20 and respectively 22', leaving aspace therebetween to ensure the engagement of sliver 18 in a suitableplanar arrangement for cutting operations thereon.

At least the track 20 is formed with a plurality of windows 32, having awidth and a height greater than the corresponding dimensions of window16 wherein said laser ray is focalized, said windows 32 being spaced atintervals D equal to the greatest common factor between the lengths oftuft fibres into which the filaments of sliver 18 are to be cut.

The whole equipment is assembled in such a way that the vertical lengthsof track 20, which obviously run in opposite directions, show alignedwindows 32 when crossing the laser ray. Similarly, said laser ray ispulsed (or pulsatorily intercepted) in synchronism with the passage ofsaid windows 32 in alignment relationship with said ray direction 14.

Moreover, the whole equipment is obviously assembled and pre-set in sucha manner that the plane wherein said sliver l8 lies, between saidapproached track lengths, is coincident with the plane wherein the laserray is focalized within said essentially rectilinear window 16.

Thus, when the equipment is operated under said alignment, focalizationand synchronism conditions, the sliver portions that are left uncoveredby said windows 32 are struck by the laser ray, as focalized in 16 andare accurately and sharply sheared across a minimum height, owing tovery small height of window 16 wherein the ray is focalized, as well asto very short pulse duration.

Obviously, when said laser pulses are synchronized at a frequencycorresponding to the passage of windows 32, the filaments of sliver 18are cut into tuft fibres having a length D. When fibres having a lengthequal to a multiple of D are required, said pulses shall be synchronizedat a frequency such as to operate only when a corresponding multiple ofwindows 32 is passed across said direction 14.

The laser ray energy in excess to that absorbed for the volatilizationof filaments may be taken-up by the downstream located track length 22.However, in order to prevent any damage to said track length 22, it canbe formed with windows and a suitably cooled screen is then fittedbehind the same and in the laser ray direction 14 to take-up saidresidual energy.

The equipment comprises further a device 34, that is connected to asuitable source of pressurized nitrogen and is formed with slit nozzles36 and 38 through which blade-shaped nitrogen jets are directed againstthe sliver 18, above and below the striking point of said laser ray.

Moreover, the equipment comprises also means wherein the tuft fibres arecollected when discharged in a direction F from said feeding tracks,such means being diagrammatically exemplified by a collecting container40; as well as means for cooling said tracks, safety and protectionmeans for the zone traversed by said laser ray, and so on.

As an example of an equipment built and operated according to thisinvention, a sliver formed by 10,000 polyester filaments each having acount of 1.5 deniers and thus with a total sliver count of 15,000deniers was cut in tuft fibres. Said sliver was fed at a speed of 500m/min. and cotton-cut sheared. The track 20 was fonned with windows atintervals D or 40 mms, and laser pulses having a wavelength of about 8microns and focalized as in 16 over a width of 20 mms were senttherethrough at a frequency of about 208 pulses per second in such amanner that the sliver 18 was struck approximately at the center of eachwindow 32. Another sliver was similarly sheared into woolen-cut tuftfibres mm and mm long by means of laser rays having a frequency equal toa half and respectively to a third of the above stated one. A sharp andconstant cutting action was obtained, with a very small portion ofwelded fibres that is due to faults in the previously carried-outfilament drawing and thermosetting operations.

A similar experiment was conducted on a sliver of polyamidic filaments(Nylon 6) which was cut by following the above procedure except thatlaser pulses having a wavelength of about 6.1 microns were used. Theresults were similarly favourable.

We claim:

1. Apparatus for cutting a sliver of textile filaments into textiletufts comprising first and second endless track means, means mountingsaid track means for rotation, at least a portion of said first trackmeans being positioned in a plane parallel to and adjacent at least aportion of said second track means for holding a length of slivertherebetween, means for rotating said track means, said means forrotating said track means moving said portions of said track means inthe same direction, whereby said length of sliver is also moved in saidsame direction in a plane parallel to said first mentioned plane; saidfirst track having a plurality of win dows therein for exposing aportion of said sliver, each of said windows having a width larger thanthat of said sliver and a height of a few microns so that the entirewidth of said portion of said sliver can be exposed in said windows;means for generating a beam of laser radiation positioned adjacent saidtrack means; and means for focusing said beam onto a part of said firsttrack means where said portion of said track means is adjacent saidportion of said second track means and in the path of said movingwindows, said means for focusing said laser beam directing said beamonto said first track means in a form having an elongated rectangularcross-section; and means for interrupting said beam when a window havinga portion of said sliver exposed therein is not positioned at the partof said first track means where said beam is focused.

2. Apparatus as claimed in claim 1 including means for emitting saidbeam of laser radiation in pulses having a pulse duration shorter thanone thousandth of a second.

3. Apparatus as claimed in claim 1 wherein said track means comprisecounter-rotating tracks and said means for rotating rotates said tracksat a speed equal to the sliver feeding speed, said windows having alength and a width greater than that of said laser beam focused on saidfirst track and spaced at intervals equal to the length of textile tuftsto be obtained.

4. Apparatus as claimed in claim 1 wherein said track means comprisecounter-rotating tracks and said means for rotating rotates said trackat a speed equal to the sliver feeding speed, said windows having alength and a width greater than that of said laser beam focused on saidfirst track and spaced at intervals a submultiple of the length of thetextile tufts to be obtained.

. 5. Apparatus as claimed in claim 3 wherein said means for generatingsaid beam of laser radiation and said track are mutually located so thatthe direction of said laser beam is coincident with an alignment ofpositions simultaneously taken by said track windows that are present inboth lengths of said first track means.

6. Apparatus as claimed in claim 3 comprising means for blowing a jet ofan oxidation preventing gas towards points located directly upstream anddownstream of the part of said first track struck by said laser beam.

1. Apparatus for cutting a sliver of textile filaments into textiletufts comprising first and second endless track means, means mountingsaid track means for rotation, at least a portion of said first trackmeans being positioned in a plane parallel to and adjacent at least aportion of said second track means for holding a length of slivertherebetween, means for rotating said track means, said means forrotating said track means moving said portions of said track means inthe same direction, whereby said length of slIver is also moved in saidsame direction in a plane parallel to said first mentioned plane; saidfirst track having a plurality of windows therein for exposing a portionof said sliver, each of said windows having a width larger than that ofsaid sliver and a height of a few microns so that the entire width ofsaid portion of said sliver can be exposed in said windows; means forgenerating a beam of laser radiation positioned adjacent said trackmeans; and means for focusing said beam onto a part of said first trackmeans where said portion of said track means is adjacent said portion ofsaid second track means and in the path of said moving windows, saidmeans for focusing said laser beam directing said beam onto said firsttrack means in a form having an elongated rectangular crosssection; andmeans for interrupting said beam when a window having a portion of saidsliver exposed therein is not positioned at the part of said first trackmeans where said beam is focused.
 2. Apparatus as claimed in claim 1including means for emitting said beam of laser radiation in pulseshaving a pulse duration shorter than one thousandth of a second. 3.Apparatus as claimed in claim 1 wherein said track means comprisecounter-rotating tracks and said means for rotating rotates said tracksat a speed equal to the sliver feeding speed, said windows having alength and a width greater than that of said laser beam focused on saidfirst track and spaced at intervals equal to the length of textile tuftsto be obtained.
 4. Apparatus as claimed in claim 1 wherein said trackmeans comprise counter-rotating tracks and said means for rotatingrotates said track at a speed equal to the sliver feeding speed, saidwindows having a length and a width greater than that of said laser beamfocused on said first track and spaced at intervals a submultiple of thelength of the textile tufts to be obtained.
 5. Apparatus as claimed inclaim 3 wherein said means for generating said beam of laser radiationand said track are mutually located so that the direction of said laserbeam is coincident with an alignment of positions simultaneously takenby said track windows that are present in both lengths of said firsttrack means.
 6. Apparatus as claimed in claim 3 comprising means forblowing a jet of an oxidation preventing gas towards points locateddirectly upstream and downstream of the part of said first track struckby said laser beam.